When producing a semiconductor device, a silicon-containing dielectric layer (e.g., SiO2 film or SiOC film) may be subjected to plasma etching using an organic film layer (e.g., photoresist) as a mask to form a contact hole and the like.
A halogen-based gas (halogen=F, I, and/or Br) that includes a fluorocarbon compound in which the atomic ratio of at least one of I and Br is 26% or less based on the total halogen content and the remainder is F, has been proposed as a process gas (etching gas) used for plasma etching (see Patent Document 1). Patent Document 1 states that damage to the resist mask can be reduced by utilizing such a halogen-based gas.
However, the halogen-based gas specifically disclosed in Patent Document 1 is a saturated compound having a long atmospheric lifetime, and lacks environmental acceptability.
Since hydrogen bromide has a sidewall protection effect, a multi-step etching technique that performs etching using hydrogen bromide before and after an etching step that utilizes fluorine gas has been widely employed.
However, a single-step plasma etching technique that utilizes a single process gas is preferable from the viewpoint of productivity as compared with a multi-step etching technique that selectively utilizes a plurality of process gases.
Since hydrogen bromide has an effect of promoting deposition of a carbon-based polymer, a plasma etching technique that utilizes hydrogen bromide in combination with a fluorocarbon (e.g., C4F8) has also been studied (see Patent Document 2).
However, the above method poses various problems (e.g., hydrogen bromide has corrosiveness to a metal and the like, and the complexity of the production process increases since it is important to control the mixing ratio of hydrogen bromide to the fluorocarbon) when industrially producing a semiconductor device or the like using the above method.
A technique that utilizes a fluorinated hydrocarbon gas in order to form a contact hole having a good shape using a single process gas has also been proposed (see Patent Document 3).